Mold for contact lens with non-rotationally symmetric rim or edge

ABSTRACT

A mold for a front curve of an ophthalmic lens includes an inner region having a non-rotationally symmetric shape, an outer region having a rotationally symmetric shape, and a continuous middle region between the inner region and the outer region. A first portion of the middle region is in contact with the inner region, defining a non-rotationally symmetric rim or edge of a front surface of the ophthalmic lens. A second portion of the middle region is in contact with the outer region and is rotationally symmetrical.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/212,542 filed on Jul. 18, 2016 that is currently pending.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a mold for a front curve of anophthalmic lens that enables manufacture of a lens with anon-rotationally symmetric rim or edge, for example, using a soft-moldedprocess.

Discussion of the Related Art

Myopia or nearsightedness is an optical or refractive defect of the eyewherein rays of light from an image focus to a point before they reachthe retina. Myopia generally occurs because the eyeball or globe is toolong or the cornea is too steep. A minus or negative powered sphericallens may be utilized to correct myopia. Hyperopia or farsightedness isan optical or refractive defect of the eye wherein rays of light from animage focus to a point after they reach or behind the retina. Hyperopiagenerally occurs because the eyeball or globe is too short or the corneais too flat. A plus or positive powered spherical lens may be utilizedto correct hyperopia. Astigmatism is an optical or refractive defect inwhich an individual's vision is blurred due to the inability of the eyeto focus a point object into a focused image on the retina. Astigmatismis caused by a non-rotationally symmetric curvature of the cornea. Anormal cornea is spherical whereas in an individual with astigmatism,the cornea is not spherical. In other words, the cornea is actually morecurved or steeper in one direction than another, thereby causing animage to be stretched out into two line foci rather than focused to asingle point. A cylindrical lens rather than a spherical lens may beutilized to resolve astigmatism. Contact lenses may be utilized tocorrect myopia, hyperopia, astigmatism as well as other visual acuitydefects.

Corneal astigmatism may be corrected using a hard or rigid gas permeablecontact lens. In this case, a fluid or tear film may exist between theposterior surface of the rigid contact lens and the cornea. This fluidor tear film follows or assumes the shape of the back surface of thecontact lens. Since the index of refraction of the fluid or tear film isnearly a match for the cornea, the corneal toricity is opticallyneutralized or reduced. In these cases, a toric lens will not berequired. However, rigid gas permeable contact lenses and hard contactlenses are generally less comfortable than soft or hydrogel contactlenses. Since soft or hydrogel contact lenses wrap around the cornea, afluid film is generally not found and the tear fluid more closelyresembles a thin film. In this case, a toric lens design may berequired.

A toric lens is an optical element having two different powers in twoorientations that are perpendicular to one another. Essentially, a toriclens has one power (spherical) for correcting myopia or hyperopia andone power (cylinder) for correcting astigmatism built into a singlelens. These powers are created with curvatures oriented at differentangles which are preferably maintained relative to the eye. Toric lensesmay be utilized in eyeglasses, intraocular lenses and contact lenses.The toric lenses used in eyeglasses and intraocular lenses are heldfixed relative to the eye by either the spectacle frame or haptics,thereby always providing optimal vision correction. However, toriccontact lenses without stabilization features may tend to rotate on theeye, thereby temporarily providing sub-optimal vision correction.Accordingly, currently utilized toric contact lenses also include amechanism to keep the contact lens relatively stable on the eye when thewearer blinks or looks around. For many high order aberrations, many ofwhich are not rotationally symmetric, positional stability andcentration are also required to provide optimal vision correction.

It is known that correction of certain optical defects may beaccomplished by imparting non-rotationally symmetric correctivecharacteristics to one or more surfaces of a contact lens such ascylindrical, bifocal, multifocal, wavefront corrective characteristicsor decentration of the optical zone. It is also known that certaincosmetic features such as print patterns, markings, and the like arerequired to be placed in a specific orientation relative to the wearer'seye. Thus each of the non-rotationally symetric contact lenses of a pairmust be maintained at a specific orientation while on the eye to beeffective. When a contact lens is first placed on-eye, it mustautomatically position, or auto-position, itself and then maintain thatposition over time. However, once the contact lens is positioned, ittends to rotate on the eye due to the force exerted on the contact lensby the eyelids during blinking as well as eyelid and tear film movement.

Maintenance of the on-eye orientation of a contact lens typically isaccomplished by altering the mechanical characteristics of the contactlens. For example, prism stabilization, including decentering of acontact lens front surface relative to the back surface, thickening ofthe inferior contact lens periphery, forming depressions or elevationson a contact lens surface, and truncating the contact lens edge, are allmethods that are utilized.

Additionally, static stabilization has been used in which the contactlens is stabilized by the use of thick and thin zones, or areas in whichthe thickness of a contact lens periphery is increased or reduced.Typically, the thick and thin zones are located in the contact lensperiphery with symmetry about the vertical and/or horizontal axes. Forexample, each of two thick zones may be positioned on either side of theoptic zone and centered along the 0-180 degree axis of the contact lens.In another example, a single thick zone positioned at the bottom of thecontact lens providing a similar weight effect, like that of prismstabilization, but also incorporating a region of increasing thicknessfrom top to bottom in order to utilize upper eyelid forces to stabilizethe contact lens may be designed. It is important to note that oldertechnical literature utilizes the term dynamic stabilization for what wemean here as static stabilization. Accordingly, for purposes of thisinvention, static and dynamic stabilization are utilizedinterchangeably.

The challenge with current stabilization zones is a tradeoff betweencontact lens stability and comfort, plus the physical limitationsassociated with increased thickness. With a static or dynamicstabilization zone, the slope of the stabilization zone is fixed in thecontact lens. Changes to the design to improve rotational speed, such asincreasing the surface slope of the stabilization zone, also increasescontact lens thickness and may adversely impact comfort. Additionally,contact lens design has to accomplish two things: (1) to rotate to theproper orientation on insertion and (2) to maintain that orientationthrough the wear period. Conventional designs require tradeoffs inperformance between these two modes.

In a newborn, the crystalline lens of the eye is somewhat soft andpliant making it extremely flexible and capable of a large degree ofaccommodation or focusing. As a person ages, the crystalline lensgradually becomes more rigid, and thus, their eyes are less able toaccommodate, or bend the natural lens, to focus on objects that arerelatively near to the observer. This condition is known as presbyopia.

A plus power lens may be utilized to restore the focusing power lost bythe crystalline lens. The plus power lens may take the form of readingglasses, bifocal glasses or trifocal glasses. Reading glasses are easilyutilized when an individual does not need refractive correction fordistance. However, distant objects will be blurry when looking throughreading glasses. If an individual is already wearing glasses for myopia,hyperopia and/or astigmatism, then the plus power may be added to theexisting glasses in the form of a bifocal or trifocal lens. Contactlenses may also be worn to address presbyopia. In one type of suchlenses, distance and near vision regions are concentrically arrangedaround the geometric center of the lens. Light passing though theoptical zone of the lens is concentrated and focused at more than onepoint in the eye. These lenses are generally used in simultaneous visionmode. In simultaneous vision, portions of the lens optical zone focusedfor distance and near are available at the same time, focusing lightfrom both object distances simultaneously. This is disadvantageous asimage quality and image contrast may be degraded.

In a segmented lens, near and distance vision regions are not concentricabout the geometric center of the lens. The wearer of segmented lensesis able to access the near vision region of the lens because the lens isconstructed to allow it to translate, or move vertically relative to thepupil of the wearer's eye. This translating lens moves vertically whenthe person wearing the lens shifts their gaze downwardly, for example,to read. This upwardly positions the near vision portion in the centerof the wearer's gaze. Substantially all of the light passing though theoptical zone may be focused at a single point in the eye based on gaze.

One type of translating lens has a truncated shape. That is, unlike mostlenses that are substantially continuously circular or oval, the lowerportion of the truncated contact lens is flattened by cutting off orshortening that part of the lens. This results in a substantially flat,thick edge at the bottom of the lens. Exemplary descriptions of suchlenses are set forth in a number of patents, including U.S. Pat. Nos.7,543,935, 7,430,930, 7,052,132, and 4,549,794. However, such arelatively flat edge may tend to reduce comfort. It is thereforedesirable to have a translating contact lens without this type of edgedesign, thereby providing improved comfort.

Contact lenses for presbyopia, astigmatism and other optical defectsgenerally require non-optical features as described herein forpositioning and maintaining the rotational orientation of the lens oneye. These features require certain tradeoffs, for example, comfort andfit for visual acuity. Accordingly, there exists a need for contactlenses with improved on-eye performance while maintaining a high degreeof comfort.

An improved fit contact lens would preferably provide improvedcentration, improved rotation and/or translation of the contact lenson-eye and improved tear exchange. By modifying the rim or edge designof a contact lens, on-eye orientation, for example, with toric lenses,may be maintained without the need for stabilization zones or similarconstructs. By modifying the rim or edge design of a contact lens,presbyopia may be addressed without the need for complicated, generalfit translating contact lenses. By modifying the rim or edge design of acontact lens, differential pressure in the post-lens tear film may beobtained, thus improving tear exchange without the need to significantlymodify the contact lens, thereby promoting improved clinical comfort.The rim shape may be optimized based on ocular anatomy, including eyelidgeometry, eyelid tension, blink movement characteristics, andcorneal/trans-limbal topography.

FIG. 1 shows a known mold 100 for the front curve of a contact lenshaving an inner region 105, and outer region 110, and a boundary region115 between regions 105 and 110. The inner region 105 is concave andcorresponds to the shape of the front surface of the contact lens. Theouter region 110 may be flat, such as a disk, and is part of the mold,but does not form any part of the front surface of the contact lens. Theouter region may have a surface feature, such as a rib or protrusion, toenable manufacturing. The boundary region 115 determines the shape ofthe contact lens rim or edge. In FIG. 1, the lens edge will be circularand flat, which means that the intersection between inner region 105 andouter region 110 is circular and every point along boundary region 115lies in a single plane. Four cross-sections are illustrated (AB, AC, AD,and AE). These four cross-sections have an identical shape because themold is rotationally symmetric with respect to an axis of symmetrypassing through point A. The front surface of the contact lens resultingfrom this mold has a circular, rotationally-symmetric edge.

A lens having a non-rotationally symmetric rim or edge presents multiplechallenges that are non-existent in a traditional lens mold. The factthat the rim or edge path is non-rotationally symmetric requires thelens mold to have customized features to achieve complete edge contact(and cut-off) between the front and back curves, while maintainingcurrent manufacturing processes. This is particularly important in avery high volume manufacturing process such as fabrication of contactlenses.

Accordingly, there is a need for lens molds that can produce lenseshaving a rim or edge that is non-rotationally symmetric using existingmanufacturing processes for lenses, such as soft contact lenses.

SUMMARY OF THE INVENTION

The mold for contact lens with non-rotationally symmetric rim or edge ofthe present invention provides a means for manufacturing lenses whichovercome the disadvantages associated with the prior art as brieflydescribed above by altering the planarity of the lens outer edge, theoverall shape or symmetry of the lens, or both.

The mold for contact lens with non-rotationally symmetric rim or edge ofthe present invention provides a means for manufacturing lenses whichovercome the disadvantages associated with the prior art as brieflydescribed above by altering the planarity of the lens outer edge, theoverall shape or symmetry of the lens, or both.

A mold for a front curve of an ophthalmic lens according to the presentinvention includes an inner region defining a front surface or curve ofan ophthalmic lens and having a non-rotationally symmetric shape and anouter region having a rotationally symmetric shape. A continuous middleregion is located between the inner region and the outer region. A firstportion of the middle region is in contact with the inner region,defining a non-rotationally symmetric rim or edge of a front surface orcurve of the ophthalmic lens. A second portion of the middle region isin contact with the outer region and is rotationally symmetrical.

The contact lenses may be manufactured utilizing existing technologieswithout any significant impact in cost over existing contact lenses. Thecontact lenses of the present invention may be utilized with any type ofcontact lens optics without additional cost and optimized to improveclinical comfort and/or physiology.

The improved fit contact lenses that may be manufactured by the mold ofthe present invention may be customized by populations, subpopulationsand/or individuals. In addition, these contact lenses may be utilizedwith any type of contact lens optics or configurations withoutadditional cost and optimized to improve clinical comfort and/orphysiology.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIG. 1 is a perspective view of a known mold for a front curve of acontact lens. The mold results in a contact lens having arotationally-symmetric rim or edge.

FIG. 2 is a perspective view of an exemplary mold for a front curve of acontact lens according to an embodiment of the present invention,showing an inner region, and outer region, and a middle region or zone.The mold results in a front curve of the lens having a non-rotationallysymmetric rim or edge.

FIG. 3A is a cross-section side view of a mold for a front curve of acontact lens according to an embodiment of the present invention, whichis affixed to a mold for a back curve of the contact lens. A middleregion or zone of the front curve mold is shown. The resulting contactlens (circled) has a rim or edge that is circular, continuous, andnon-planar.

FIG. 3B is a top view of the molds of FIG. 3A with four cross sectionsAB, AC, AD, AE and illustrating the middle region or zone according tothe present invention.

FIG. 3C is a side view comparison of cross sections AB and AD to crosssections AC and AE of the molds of FIGS. 3A-B. The rim or edge of thecontact lens does not lie in the same plane as shown by the dotted line.

FIG. 4A is a top view of contact lens molds with the four cross sectionsAB, AC, AD, and AE and illustrating a middle region or zone according tothe present invention. The resulting contact lens has a non-circular,continuous, and non-planar rim or edge.

FIG. 4B is a side view comparison of cross-sections AB and AD to crosssections AC and AE of the the molds of FIG. 4A. The rim or edge of thecontact lens does not lie in the same plane as shown by the dotted line.

FIG. 5A is a top view of contact lens molds with the four cross sectionsAB, AC, AD, and AE and illustrating a middle region or zone according tothe present invention. The resulting contact lens has a non-circular,non-continuous, and non-planar rim or edge.

FIG. 5B is a side view of cross sections AB and AD of the contact lensmolds of FIG. 5A. FIG. 5C is a side view comparison of cross section AEto cross section AC of the molds of FIG. 5A. The rim or edge of thecontact lens does not lie in the same plane as shown by the dotted line.

FIG. 6A is a top view of contact lens molds with the four cross sectionsAB, AC, AD, and AE and illustrating a middle region or zone according tothe present invention. The resulting contact lens has a non-circular,continuous, and planar rim or edge.

FIG. 6B is a side view comparison of cross sections AB and AD to crosssections AC and AE of the molds of FIG. 6A. The rim or edge of thecontact lens lies in the same plane as shown by the dotted line.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A contact lens is defined by a front surface, a back surface or basecurve and a rim or edge. For the purpose of the present invention, theshape of the rim or edge may be described by circularity, continuity,and planarity. A rim or edge is circular if the rim or edge projectiononto a given plane is a circle, otherwise the rim or edge isnon-circular. A rim or edge is continuous if the edge is a curve thatmay be classified as at least a class C1 curve. Continous in this senseis defined as the shape being smooth and closed, which means that theslope, i.e. the first derivative of the curve is continous, otherwisethe rim or edge is discontinuous. A rim or edge is planar if it liesfully in a single plane, otherwise it is non-planar.

The present invention relates to a mold for a front curve of anophthalmic lens, such as a contact lens, that enables manufacture of alens with a non-rotationally symmetric rim or edge. In particular, thefront curve mold according to the present invention allows for the useof an existing soft-molded manufacturing process for soft contactlenses. The mold for the front curve according to the present inventionhas a middle region or zone that maintains surface continuity betweendifferent mold regions, while providing for a lens having anon-rotationally symmetric rim or edge. In exemplary embodiments, thefront curve mold provides for a contact lens having rim or edge that isat least one of non-circular, non-continuous, non-planar, or anycombination thereof.

Referring now to FIG. 2, a front curve lens mold 200 according to thepresent invention comprises an inner region 205, which forms the frontcurve of the resulting lens, and an outer region 210, which does notform any part of the resulting lens. Inner region 205 has anon-rotationally symmetric shape and outer region 210 has a rotationallysymmetric shape. Unlike the lens mold shown in FIG. 1, the inner region205 and the outer region 210 do not intersect.

According to the present invention, a middle region or zone 215 islocated between the inner region 205 and the outer region 210. In orderto ensure surface continuity of the mold 1) a first portion of middleregion 215 is in contact with the inner region 205, thereby defining anon-rotationally symmetrical rim or edge 220, and 2) a second portion ofmiddle region or zone 215 is in contact with the outer region 210 anddefines a rotationally symetric rim or edge 225.

According to the present invention, the middle region or zone 215 doesnot have a known three-dimensional (3D) geometric form. Thus, the middleregion 215 does not have a close form equation. Rather, the middleregion 215 may be described as a two-dimensional (2D) variable surfacewith a geometry that varies by meridian. That is, the shape may bedifferent in one or more cross-sections. Another way to define thismiddle region 215 is to define the two dimensional variable surface asthe result of connecting the rotationally symmetric edge 225, which liesin a single plane, to the desired non-rotationally symmetrical lens edgegeometry, for example, edge 220, which may be non circular, non planarand non continuous and connect these two edges with a line, a curve, apolynomial, or a combination of multiple curves that results in avariable surface that facilitates mold halves interaction, includingmold insertion, molding and mold removal. Although cross-sections AB,AC, AD, and AE are illustrated in the figures, it will be understoodthat additional meridians may be used to describe the variable surfaceof the middle region. The shape of the portion of the middle region thatcontacts the inner region depends on the desired shape of a resultinglens rim or edge. In specific embodiments, the middle region may bedefined by a line, a curve, a polynomial, or a combination of multiplecurves in order to facilitate the molding process.

Referring now to FIG. 3A, a side view of a portion of the front curvecontact lens mold 300 according to the present invention and a backsurface contact lens mold 303 is shown. Inner region 305 and outerregion 310 of the front curve mold 300 are shown. The resulting contactlens located between the molds is circled. In this exemplary embodiment,middle region or zone 315 is a two-dimensional line. The contact lenshas a rim or edge 320 that is circular, continuous, and non-planar.

FIG. 3B is a top view of the molds 300, 303 shown in FIG. 3A, withmiddle region 315, lens rim 320, and cross sections AB, AC, AD, and AEillustrated.

FIG. 3C shows side view comparisons of portions of cross sections AB &AD to cross sections AC & AE of the molds of FIGS. 3A-3B. The dottedline shows that the lens rim or edge 320 does not lie in a single plane.

Referring now to FIG. 4A, a top view of front and back molds for acontact lens having a non-circular, continuous, and non-planar rim oredge 420 is shown. A middle region 415 of the front curve mold accordingto the present invention is shown, along with cross-sections AB, AC, AD,and AE.

FIG. 4B shows side view comparisons of front curve contact lens mold 400and back curve mold 403 for cross sections AB & AD to that of crosssections AC & AE of the molds of FIG. 4A. Inner region 405, outer region410, and middle region or zone 415 of the front curve mold are shown.The dotted line shows that the lens rim or edge 420 of cross sections AB& AD is in a different plane than the lens rim or edge 420 of crosssections AC & AE due to the fact that the rim or edge is non-circularand non-planar.

Referring now to FIG. 5A, a top view of front and back molds for acontact lens having a non-circular, non-continuous, and non-planar rimor edge 520 is shown. A middle region 515 according to the presentinvention is shown, along with cross-sections AB, AC, AD, and AE.

FIG. 5B shows side view comparisons of front curve contact lens mold 500and back curve contact lens mold 503 for cross sections AB & AD of FIG.5A. Inner region 505, outer region 510, and middle region 515 are shown.FIG. 5C shows side view comparisons of cross section AE, to that ofcross section AC both of FIG. 5A. The dotted line shows that the lensedge or rim 520 of cross section AC is in a different plane than thelens rim or edge 520 of cross section AE due to the fact that the rim oredge is non-circular, non-continuous, and non-planar.

Referring now to FIG. 6A, a top view of molds for a contact lens havinga non-circular, continuous, planar rim or edge 620 is shown. A middleregion 615 of a front curve mold according to the present invention isshown, along with cross-sections AB, AC, AD, and AE.

FIG. 6B shows side view comparisons of front curve contact lens mold 600and back curve contact lens mold 603 for cross sections AB & AD to crosssections AC & AE of the molds FIG. 6A. Inner region 605, outer region610, and middle region or zone 615 are shown. The dotted line shows thatthe lens edge or rim 620 of cross sections AB & AD is in the same planeas the lens rim or edge 620 of cross sections AC & AE due to the factthat the rim or edge of the contact lens is planar.

Although shown and described is what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

What is claimed is:
 1. A mold pair for forming a contact lenstherebetween, the contact lens having a front surface and an opposingback surface that meet at a lens edge, comprising: a back mold having aconvex, rotationally symmetric surface; a front mold having an innerregion, an outer region and a middle region positioned between andconnecting said inner and outer regions, wherein the front mold furthercomprises an inner region having a concave portion bounded by acontinuous, non-planar outer peripheral edge, wherein the concaveportion and outer peripheral edge are sized and shaped to define saidfront surface and lens edge of said contact lens; an outer region havinga rotationally symmetric shape and which does not influence a shape ofsaid contact lens, said outer region lying in a single plane and havinga continuous, circular, rotationally symmetric inner periphery, whereinsaid inner periphery of said outer region does not intersect with saidouter peripheral edge of said inner region; and a middle regionpositioned between and connecting the outer peripheral edge of the innerregion and the inner periphery of said outer region, the middle regioncomprising a continuous two-dimensional variable surface; wherein saidfront and back molds are adapted to be positioned relative to oneanother such that the outer peripheral edge of said inner region of saidfront mold is in constant contact with said convex surface of said backmold, and a space between said front and back molds defines a shape ofsaid contact lens to be formed.